No reason was given for El-Erian's resignation, but it comes after the company's now-US$237 billion Pimco Total Return, the world's largest bond fund, saw disappointed investors pull out US$41 billion last year.

Pimco, which had US$1.97 trillion in assets under management at the end of September 2013, said that El-Erian will be replaced as CEO by Douglas Hodge, currently managing director of Pimco's Newport Beach office and the company's chief operating officer.

Pimco's founder William Gross will remain chief investment officer.

“Over the past years, Pimco has achieved an outstanding performance in asset management,” said Jay Ralph, a member of the Allianz board, in a statement.

“It speaks for the strength and diversity of Pimco that all positions can be filled by internal candidates. With this continuity we are well prepared for the future.”

El-Erian will remain on the Allianz International Executive Committee and advise the Allianz board, the company said.

El-Erian, 55, spent 15 years at the International Monetary Fund, and then became a managing director of Citigroup, before joining Pimco in 1999.

He left the company to become president and chief executive of the company that manages Harvard University's huge endowment, and then rejoined Pimco in 2007.

In 2011 he was often mentioned as a possible candidate to lead the IMF after the resignation of managing director Dominique Strauss-Kahn.

Gross called El-Erian “a great leader, business builder and thought leader for Pimco and its clients.”